The present invention relates generally to hydraulically actuated fuel injection systems. More particularly, the present invention relates to devices for minimizing pressure fluctuations in the actuating fluid system.
Hydraulically actuated, electronically controlled unit injection systems (HEUI) injectors require a source of high pressure actuating fluid. Each of the fuel injectors of an engine is typically serviced by a common high pressure actuating fluid rail. The rail usually runs along the head of a bank of cylinders. In the past, tubular connectors have extended between the rail and individual injectors for conveying high pressure actuating fluid to the injector. It is important for both engine performance and engine noise emission considerations that each injector have a stable source of high pressure actuating fluid.
Each HEUI injector has an internal actuator that turns on and off the high pressure actuating fluid to the injector. The cycling of the actuator, at least once every injection event, may cause a water hammer effect that is transmitted through the connector to the rail. The water hammer effect causes pressure instability in the rail and is also a source of objectionable engine noise emission. In the prior art, for V-form engines, a check valve or check valves have been interposed in the plumbing that connects the two high pressure rails serving each bank of cylinders. Such a design is the subject of U.S. Pat. No. 5,168,855 to Stone and an exemplary schematic of this design is presented in prior art FIG. 9. The prior art actuating fluid system 400 includes a high pressure pump 402 that draws actuating fluid from a low pressure reservoir 404. A rail pressure control valve 406 monitors (via sensor communication 407) and controls the maximum pressure in the rails by dumping pressure back to the reservoir 404 via fluid ling 408 under certain conditions. The design of the prior art system 400 is for a V form engine of six cylinders (and, in fact, is inapplicable to an engine with a single bank of cylinders serviced by a single rail). Accordingly, a check valve 410 is disposed in the fluid line to the left rail 412 and a check valve is disposed in the fluid line to the right rail 414. Each of the rails 412, 414 supplies high pressure actuating fluid directly to the three injectors 416, 418 on the bank of cylinders served by the respective rail 412, 414. A pressure fluctuation emanating from an injector 416 is isolated for the right rail 414 and the injectors 418 serviced by the right rail by the check valves 410. A pressure fluctuation emanating from a certain injector 416 is translated to the left rail 412 and may affect the operation of the other two injectors 416. The check valves 410 provide no isolation in the last mentioned case. This last mentioned case is analogous to an inline engine having a single bank of cylinders.
While the mechanization of the ""855 patent may partially alleviate cross talk between the two high pressure actuating fluid rails of a V-type engine, the mechanization does nothing to deal with the instabilities induced in a single rail by all of the injectors serviced by that rail. Accordingly, there is a need in the industry to minimize the pressure pulses reaching a high pressure actuating fluid rail from a specific injector. Such means of control should act to stabilize the pressure in the affected high pressure actuating fluid rail as well as minimizing emission noise emanating from the rail due to the presence of the water hammer effect caused by the individual injectors.
Additionally, as indicated above, the mechanization of the xe2x80x2855 patent simply does not address the problem of an inline engine with a single high pressure actuating fluid rail. All of the injectors serviced by such a rail, typically six or more, are free to send pressure waves through the high pressure actuating rail. Accordingly, there is a further need in the industry for a means to correct the aforementioned problem as it exists in inline engines as well as the problem existing in V-type engines.
The connector assembly of the present invention substantially meets the aforementioned needs of the industry. Each injector serviced by a high pressure actuating fluid rail is in fluid communication with the rail by means of a connector assembly of the present invention. Each connector assembly of the present invention includes a check valve that is seated by the pressure of the water hammer effect caused by the closing of the injector actuator. Such closing substantially prevents transmission of the water hammer effect to the rail. By containing the water hammer effect, the noise emitted from the rail is substantially reduced. Further, pressure of the high pressure actuating fluid in the rail is substantially stabilized, thereby improving the performance of each of the injectors serviced by the rail.
A further benefit of the connector assembly of the present invention is that it can be utilized to control injector inlet volume and pressure. Such control is beneficial in minimizing the quantity of fuel injected during the pilot injection portion of an injection event. Such control acts to minimize noise emissions from the engine and to improve drivability.
The present invention is a connector assembly and the actuating system including the connector assembly, the connector assembly for fluidly coupling an actuating fluid rail to a fuel injector, the actuating fluid rail conveying a quantity of actuating fluid, the fuel injector having an actuating fluid inlet, the connector assembly includes a check valve operably disposed in a connecting member for controlling the flow of actuating fluid between the actuating fluid rail and the fuel injector. The connecting member has a fluid passageway defined therein, the fluid passageway being in fluid communication with the actuating fluid rail and the fuel injector actuating fluid inlet. The present invention is further a method of minimizing negative pressure effects caused by operation of a fuel injector on the actuating fluid in an actuating fluid rail and a method of providing a high pressure actuating fluid flow from a high pressure pump to a plurality of fuel injectors of a diesel engine.